This paper presents for the first time results on winds, tides, gradients of horizontal winds, and momentum fluxes at mesosphere and lower thermosphere (MLT) altitudes over southern Patagonia, one of the most dynamically active regions in the world. For this purpose, measurements provided by SIMONe Argentina are investigated. SIMONe Argentina is a novel multistatic specular meteor radar system that implements a SIMONe (Spread Spectrum Interferometric Multistatic meteor radar Observing Network) approach, and that has been operating since the end of September 2019. Average counts of more than 30000 meteor detections per day result in tidal estimates with statistical uncertainties of less than 1 m/s. Thanks to the multistatic configuration, horizontal and vertical gradients of the horizontal winds are obtained, as well as vertical winds free from horizontal divergence contamination. The vertical gradients of both zonal and meridional winds exhibit strong tidal signatures. A diurnal pattern can also be observed in the vertical winds during certain days. Mean momentum fluxes are estimated after removing the effects of mean winds using a four-hour, eight-kilometer window in time and altitude, respectively. Reasonable statistical uncertainties of the momentum fluxes are obtained after applying a 28-day averaging. Therefore, the momentum flux estimates presented in this paper represent monthly mean values of waves with periods of four hours or less, vertical wavelengths shorter than eight kilometers, and horizontal scales less than 400 km.

We present a method for estimating incident photoelectrons’ energy spectra as a function of altitude by combining global scale far-ultraviolet (FUV) and radio-occultation (RO) measurements. This characterization provides timely insights important for accurate interpretation of ionospheric parameters inferred from the recently launched Ionospheric Connection Explorer (ICON) observations. Quantification of photoelectron impact is enabled by the fact that conjugate photoelectrons (CPEs) directly affect FUV airglow emissions but not RO measurements. We demonstrate the technique for the estimation of photoelectron fluxes and their spectra by combining coincident ICON-FUV and COSMIC2 measurements and show that a significant fraction of ICON-FUV measurements are affected by CPEs during the winter solstice. A comparison of estimated photoelectron fluxes with the SAMI2-PE model is used to gain further insights into the estimation method and reveals consistent values at low latitudes, while the results suggest that the model might be overestimating photoelectron fluxes by $\sim$10\% at mid latitudes.

The mesosphere and lower thermosphere (MLT) region is dominated globally by dynamics at various scales: planetary waves, tides, gravity waves, and stratified turbulence. The latter two can co-exist and be significant at horizontal scales less than 500 km, scales that are difficult to measure. This study presents a recently deployed multi-static specular meteor radar system, SIMONe Peru, which can be used to observe these scales. The radars are positioned at and around the Jicamarca Radio Observatory, which is located at the magnetic equator. Besides presenting preliminary results of typically reported large scale features, like the dominant diurnal tide at low latitudes, we show results on selected days of spatially and temporally resolved winds obtained with two methods based on: (a) estimation of mean wind and their gradients (gradient method), and (b) an inverse theory with Tikhonov regularization (regularized wind field inversion method). The gradient method allows improved MLT vertical velocities and, for the first time, low-latitude wind field parameters such as horizontal divergence and relative vorticity. The regularized wind field inversion method allows the estimation of spatial structure within the observed area and has the potential to outperform the gradient method, in particular when more detections are available or when fine adaptive tuning of the regularization factor is done. SIMONe Peru adds important information at low latitudes to currently scarce MLT continuous observing capabilities. Results contribute to studies of the MLT dynamics at different scales inherently connected to lower atmospheric forcing and E-region dynamo related ionospheric variability.